Help!!
12-29-2016, 04:08 PM
#17
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
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Re: Help!!
The GM PCM uses feedback from the O2 sensors, in closed loop, to trim the A/F ratio, and hold it at 14.7:1 for normal/part load driving. There is a complex system, using a grid of "cells", defined by RPM and engine load (MAP), for each bank of the engine. It will correct for vacuum leaks, low fuel pressure, dirty MAF sensor, etc..... anything that would alter the A/F ratio. The cats are designed to work with the PCM toggling the A/F ratio back and forth on either side of 14.7:1. And, it also keeps your gas mileage decent, prevents running rich and washing down the cylinder walls, running lean and causing knock (detonation).
You could delete the pre-cat O2 sensors, and run it in open loop, but you could have issues with fuel economy, emissions, and performance. "Sims" are generally only used in the OBD-2 cars (1996 and up) that have after-cat O2 sensors to monitor the cat performance. If you delete the cats, you either need sims for the after-cat sensors, or have the after cat sensors and codes tuned out of the PCM.
As noted above, there's a good chance your backfire is caused by the open header collectors, exposing the O2 sensors to air backwash. That causes the sensors to read lean, and the PCM dumps in extra fuel.
You could delete the pre-cat O2 sensors, and run it in open loop, but you could have issues with fuel economy, emissions, and performance. "Sims" are generally only used in the OBD-2 cars (1996 and up) that have after-cat O2 sensors to monitor the cat performance. If you delete the cats, you either need sims for the after-cat sensors, or have the after cat sensors and codes tuned out of the PCM.
As noted above, there's a good chance your backfire is caused by the open header collectors, exposing the O2 sensors to air backwash. That causes the sensors to read lean, and the PCM dumps in extra fuel.
12-30-2016, 08:44 AM
#18
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Thread Starter
Join Date: Dec 2016
Posts: 20
Re: Help!!
The GM PCM uses feedback from the O2 sensors, in closed loop, to trim the A/F ratio, and hold it at 14.7:1 for normal/part load driving. There is a complex system, using a grid of "cells", defined by RPM and engine load (MAP), for each bank of the engine. It will correct for vacuum leaks, low fuel pressure, dirty MAF sensor, etc..... anything that would alter the A/F ratio. The cats are designed to work with the PCM toggling the A/F ratio back and forth on either side of 14.7:1. And, it also keeps your gas mileage decent, prevents running rich and washing down the cylinder walls, running lean and causing knock (detonation).
You could delete the pre-cat O2 sensors, and run it in open loop, but you could have issues with fuel economy, emissions, and performance. "Sims" are generally only used in the OBD-2 cars (1996 and up) that have after-cat O2 sensors to monitor the cat performance. If you delete the cats, you either need sims for the after-cat sensors, or have the after cat sensors and codes tuned out of the PCM.
As noted above, there's a good chance your backfire is caused by the open header collectors, exposing the O2 sensors to air backwash. That causes the sensors to read lean, and the PCM dumps in extra fuel.
You could delete the pre-cat O2 sensors, and run it in open loop, but you could have issues with fuel economy, emissions, and performance. "Sims" are generally only used in the OBD-2 cars (1996 and up) that have after-cat O2 sensors to monitor the cat performance. If you delete the cats, you either need sims for the after-cat sensors, or have the after cat sensors and codes tuned out of the PCM.
As noted above, there's a good chance your backfire is caused by the open header collectors, exposing the O2 sensors to air backwash. That causes the sensors to read lean, and the PCM dumps in extra fuel.
12-30-2016, 10:02 AM
#19
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Join Date: Jul 2002
Location: Kissimmee, Fl, USA
Posts: 1,942
Re: Help!!
So i could put cats back in and put the o2 sensors back and then I'd probably just run straight pipe from the cats if i need to run the cats to make the car run right ill put those babies back on it, I don't have to worry about emmisions so cats will just help with noise lol
Look, the O2 sensors on the OBD1 cars, 93,94 and 95, have NOTHING to do with the catalytic converters. They have everything to do with engine management and must be connected whether or not there are cats installed. The car will run perfectly well with or without the cats (the OBD1 PCM doesn't even know they're there) as long as you move the exhaust exit away from the O2 sensors.
Does that make sense?
01-01-2017, 10:13 AM
#21
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Join Date: Dec 2016
Posts: 20
Re: Help!!
Do you have more than one cat? Most 95 cars came with a single cat...I think it was California emissions that necessitated a second cat.
Look, the O2 sensors on the OBD1 cars, 93,94 and 95, have NOTHING to do with the catalytic converters. They have everything to do with engine management and must be connected whether or not there are cats installed. The car will run perfectly well with or without the cats (the OBD1 PCM doesn't even know they're there) as long as you move the exhaust exit away from the O2 sensors.
Does that make sense?
Look, the O2 sensors on the OBD1 cars, 93,94 and 95, have NOTHING to do with the catalytic converters. They have everything to do with engine management and must be connected whether or not there are cats installed. The car will run perfectly well with or without the cats (the OBD1 PCM doesn't even know they're there) as long as you move the exhaust exit away from the O2 sensors.
Does that make sense?
01-01-2017, 10:58 AM
#23
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,648
Re: Help!!
Are you saying your header collectors do NOT have O2 bungs? Your earlier post said an O2 sensor delete was in your future. Where are they located now?
The correct location is in the collectors. You want to keep the sensors as close as possible to the engine, in a location where they will see a mix of exhaust from all 4 cylinders in that bank.
The correct location is in the collectors. You want to keep the sensors as close as possible to the engine, in a location where they will see a mix of exhaust from all 4 cylinders in that bank.
01-01-2017, 01:31 PM
#26
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Join Date: Jul 2002
Location: Kissimmee, Fl, USA
Posts: 1,942
Re: Help!!
I'm done....
Last edited by bw_hunter; 01-01-2017 at 01:34 PM.
01-01-2017, 02:02 PM
#27
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Join Date: Dec 2016
Posts: 20
Re: Help!!
I was just saying any true info or good opinions would be appreciated about anything on these cars not necessarily just the topic of this thread I don't know why you're getting salty that wasn't even focused toward you or anyone but sorry you're butt hurt
01-01-2017, 02:08 PM
#28
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Join Date: Dec 2016
Posts: 20
Re: Help!!
I guess proof was the wrong way to say it. I just want honest and helpful opinions to help me learn about the LT1 because this is my first one and everyone on this forum and this thread has helped me learn more than I could've on my own ever, I'm not here to upset people or make people mad I just want to learn about these cars, get help and give any advise I can from any of my personal experiences with my car so I humbly apologize if what I said offended anybody I just didn't say it the way it was meant
01-01-2017, 10:18 PM
#29
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,648
Re: Help!!
I had the same reaction. We're trying to help you learn. I tried to give you detailed info on why you needed the pre-cat O2 sensors, but you appeared to ignore it because you either didn't understand me or didn't believe me. Not getting "salty". Just trying to explain why someone might simply not respond to requests for help in the future. There are way more people here looking for help than there are people qualified to give accurate, knowledgeable help.
01-02-2017, 02:52 AM
#30
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Join Date: Dec 2016
Posts: 20
Re: Help!!
I had the same reaction. We're trying to help you learn. I tried to give you detailed info on why you needed the pre-cat O2 sensors, but you appeared to ignore it because you either didn't understand me or didn't believe me. Not getting "salty". Just trying to explain why someone might simply not respond to requests for help in the future. There are way more people here looking for help than there are people qualified to give accurate, knowledgeable help.